Field of the Invention
The present invention concerns, an apparatus for conveying a sheet-formed item, the apparatus being a through-flow apparatus arranged after a digital printing unit, and a conveyor belt and before another coating or printing unit, the apparatus including an inlet side and an outlet side, wherein the apparatus between inlet side and the outlet side includes a set of conveying means, e.g., one, two or more longitudinal conveyor belts, for moving items in a conveying direction.
The invention further concerns a method for regulating an apparatus for conveying a sheet-formed item, the apparatus being a through-flow apparatus arranged after a digital printing unit and before another coating or printing unit, the apparatus including an inlet side and an outlet side, wherein the apparatus between inlet side and the outlet side includes a set of conveying means, e.g., one, two or more longitudinal conveyor belts, for moving items in a conveying direction.
Description of Related Art
It is commonly known to perform printing or application of coating/lacquer on already printed sheets, after which the sheets are passed through a drying station and subsequently stacked in a so-called “stacker”. The sheets are alternatively passed directly to other functions via a suitable conveyor belt to, e.g., a punching operation. The sheets typically come from a kind of printing unit, e.g., digital printing unit, where the primary printing is performed, and the sheets are then moved through a coating unit where the relevant areas on each sheet are applied a coating. The speed at which these processes are performed are determined by the speed of the printing unit itself which thereby determines the speed of the rest of the plant.
When printing on sheets at a given speed, this also means that respective sheets run through the rest of the system with a given spacing between individual sheets corresponding to the spacing arising during feeding of the printing unit. This also means that the sheets are received and coated with a given spacing and subsequently passed through a drying station at the same speed and with the same spacing. In order to perform coating exactly at the areas desired to be coated, it is necessary to ensure that individual sheets are fixed precisely laterally (side register) and longitudinally (length register), presenting some challenges to the prior art. One solution could be to apply a coating on a larger area on the sheet in order to ensure that all print is covered by a coating. In some cases this may be possible, but requires more coating/lacquer, more drying and also meaning that a partial and accurate coating cannot be performed on a given print.
In order to achieve optimal and sufficient drying of the coated sheets before stacking, the process step with the drying station is particularly required to perform the necessary evaporation from the coating in the space actually available between the coating unit and the stacker. This spacing may of course be adapted according to need, but will soon be space-consuming which is not expedient as this in principle will require larger production areas.
In order to avoid too long drying stations, another solution is typically used, namely to mount more and/or more powerful heat sources and/or UV lamps which then can take care of the drying within the available time and distance. There is, however, an increasing desire to minimize the energy consumption in a drying station in order to optimize the total costs of performing the coating as well as the drying actions. As indicated above, there is also a desire for minimizing the space used by such a drying station.